Acalyphes

Acalyphes (singular: Acalyphe) is a term used in zoology, specifically in the classification of certain invertebrates. It historically referred to a division or group within the phylum Cnidaria, often used to describe jellyfish. However, the term is largely outdated and no longer used in modern scientific classifications.

Historically, "Acalyphes" encompassed jellyfish-like cnidarians that lacked a velum, a shelf-like structure found on the margin of the bell of some other jellyfish groups (e.g., Hydrozoa). This absence of a velum was a primary defining characteristic. Groups often included under the Acalyphes umbrella were Scyphozoa (true jellyfish) and sometimes certain Siphonophorans.

The usage of "Acalyphes" has declined due to advancements in understanding cnidarian phylogeny through molecular biology and detailed morphological studies. Modern classification systems rely on a more nuanced understanding of evolutionary relationships, leading to the adoption of different taxonomic structures and groupings. The term lacks the precision needed for contemporary systematic zoology. Current classification schemes typically categorize cnidarians based on features like life cycle complexity, medusa/polyp dominance, and specific anatomical characteristics beyond the simple presence or absence of a velum. Therefore, "Acalyphes" is generally considered obsolete in scientific discourse.